In the prior art combination rotary machines for sheet metal bending have long been in use. They comprise upper and lower rollers spaced close enough together to press on upper and lower sides of a piece of sheet metal to cause it to move through the space between the rollers. There are many thousands of such machines in use and special sets of rollers are available for making seams which have been primarily the seams of the type of the Pittsburgh lock seam, although for a period of approximately 15 years another kind of roller for making seams called a button lock seam have been on the market.
These types of seams have an elongated pocket into which the edge of another piece of metal is to be inserted in making a joint.
It has been necessary, in all sheet metal shops that I have been in, or heard of, that great manual labor be involved in the use of a screwdriver driven by a hammer to wedge apart the very close side walls of the elongated pocket or crevice.
Taking great time and with much manual labor, at expensive skilled tradesman's wages, workmen drive the screwdriver into the pocket, pry the pocket walls apart, then reinsert the screwdriver into the pocket a little further along the pocket and pry again. It is a slow, tedious, boring job. It produces a crude result because of the uneven appearance of the metal being bent in the points where the screwdriver has been inserted.
Machines have been made to eliminate much of this hand-labor by using a spreading disc or a spreading wheel mounted on a costly special frame to engage in the elongated crevice or pocket of the seam as sheet metal is rotated between rollers to propel it past the spreading wheel. One such machine was proposed in a U.S. Pat. No. 2,146,659, issued Feb. 7, 1939, to A. A. Stewert, entitled: SEAM PRECISION TOOL.
A second proposal is found in U.S. Pat. No. 2,334,407 issued Feb. 16, 1943, to C. H. Grebe, titled: LOCK OPENER, also having a costly special frame.
A third proposal of such a machine is to be found in U.S. Pat. No. 2,479,200, issued Aug. 16, 1949 to W. Birks, and titled: APPARATUS FOR OPENING SHEET METAL SEAM LOCKS.
The Birks machine, like those of Stewert and Grebe, also required a special frame. This meant that these machines represented a complete and full investment, whereas it is an object of this invention to provide a way to mount the spreading wheel on a carrier which is able to fit the horizontal spindle of a common combination rotary machine. Such spindles extend horizontally beneath and spaced from an upper part of the frame of such machines.
Because combination rotary machines for making seams are used in heavy sheet metal bending shops as a basic tool, therefore, this invention makes it possible to make use of the many, many thousands of these machines for the purpose of seam lock spreading so as to eliminate the need for handbending by a screwdriver.
An objective is to provide a seam lock opening machine which makes use of the great investment in combination rotary machines that has already been made so as to provide fast seam opening at the cost of purchase of only two special rollers and a spreading wheel carrier.
Another objective is to provide a machine that can be easily adjusted and that is of strong and durable construction for heavy-duty work. This is important because experiment with the Birks machine in my own shop has shown me that it has been easier to use a screwdriver, even though screwdriver seam opening is slow and very tiring, becoming slower and slower as the arms and hands become more and more fatigued, easier, that is, except on very thin sheet metal.
It is because of the above stated disadvantages of the Birks machine that I have found that none of them are to be found in the sheet metal bending shops that I have known, with the exception of the Birks machine that has been unused in my shop for many years except on very light metal.
A further object. is to provide roller and spreader carrier adaptation for existing combination rotary machines. which will not only open a Pittsburgh seam lock, but will also open a button lock.